Angry Bear has a post up (actually several posts) which indisputably show that you're better off, from an economic standpoint, to vote Democratic. I'm not going to review all the measures or posts here, you can do that by reading them. Better yet, bookmark them for those arguments with conservatives who are quite sure the opposite is true.

A few of the measures looked at are GDP, median wage growth, stock market returns, deficits and unemployment. Kevin Drum has further insights on the same topic, again good bookmarks to have. Who knows exactly why, but it's clearly not just a random occurrence. Drum guesses it has to to with Democratic policies favoring the masses rather than Republican policies pandering to the elite, particularly near elections. I think I could agree with that.